-LRB- CNN -RRB- -- People along the Texas coast were leaving home or planning to evacuate Thursday as Hurricane Ike churned toward them , slowly intensifying on its march west .

Forecasters say the storm could slam into the Texas coast -- south of Galveston -- as a powerful Category 3 storm late Friday or early Saturday .

Mandatory and voluntary evacuations were planned or underway in at least seven coastal counties .

Aransas County , on the eastern coast of Texas , has ordered a mandatory evacuation of all nonessential government employees , becoming the latest county in the state to urge residents to flee .

In Galveston , city officials ordered mandatory evacuations for part of the island town beginning at 7 a.m. Thursday . The rest of the town will be under a voluntary evacuation order . Only residents will be required to evacuate on the western end of the island .

Mayor Lyda Ann Thomas defended that , saying current models call for Galveston to be hit with winds and rain only equivalent to a Category 1 hurricane .

`` We do not intend to evacuate Galveston Island , '' she said . `` It 's the last thing we want to do . Our job is to protect lives and property , -LSB- and -RSB- right now we feel that sheltering in place is the best action for our citizens to take . ''

Farther up the Gulf Coast and closer to where the National Hurricane Center predicts a direct hit , Brazoria County ordered a mandatory evacuation to begin at 8 a.m. Thursday . Some other Texas localities have ordered mandatory evacuations , while others have left the decision to depart up to residents .

As of 5 a.m. ET Thursday , the Category 2 storm -- with top sustained winds near 100 mph -- was about 620 miles east of Brownsville , Texas , and about 285 miles southeast of the Mississippi River , the hurricane center said . Track the storm ''

Hurricane-force winds extended out up to 115 miles from the storm 's center , and tropical storm-force winds extended out up to 255 miles forecasters reported .

About 15,000 residents were leaving Galveston 's Brazoria County Wednesday after a mandatory evacuation order was issued at 10 a.m. CT -LRB- 11 a.m. ET -RRB- governing one ZIP code -- 77541 -- and residents throughout the county with special needs .

Galveston City Manager Steve LeBlanc issued a warning to residents of the city 's West End , citing forecasters ' estimates that the area could get tides of 6 feet above normal if the storm arrives there . The West End is the area of Galveston most susceptible to flooding , LeBlanc said .

Other Brazoria residents were being allowed to remain as of 6 p.m. ET .

In Matagorda County , southwest of Galveston , officials ordered a mandatory evacuation for all areas except the cities of Bay City and Van Vleck .

The evacuation must be completed by at 6 p.m. -LRB- 7 p.m. ET -RRB- Thursday . Galveston is likely to experience a high tidal surge , officials said , urging people living in low-lying areas or mobile homes to get out soon .

`` One of the things that the public has to understand if they decide to stay , there will be a period of time during this storm when they will absolutely be on their own , '' Brazoria County Sheriff Charles Wagner said .

`` There will be no medical services ; there will be no fire department ; there will be no law enforcement , groceries , gasoline , drugs , electricity . ''

The center issued a tropical storm warning from the Mississippi River 's mouth to Cameron , Louisiana , and a hurricane watch from Cameron to Port Mansfield , Texas , about 60 miles south of Brownsville . Tropical storm warnings mean winds of 39 to 73 mph -LRB- 63 to 118 kmh -RRB- are expected within a day , and a hurricane watch means winds of 74 and higher are expected within 36 hours .

`` Hurricane Ike is now in the Gulf of Mexico and making its approach toward our coast , '' Gov. Rick Perry said in a statement . `` The next few days will be crucial for residents to follow the direction of local leaders and to take the necessary steps to protect themselves and their families . ''

Perry put 7,500 National Guard members on standby this week , his office said , and issued a disaster declaration for 88 counties .

About 1,350 buses , several ambulances and paramedic buses were available to support evacuations . The vehicles were positioned near Houston , Matagorda County , Nueces County and Victoria County , the governor 's office said .

President Bush declared an emergency in the state , making federal funds available for the state to prepare for the storm .

Corpus Christi officials also began the evacuation process for residents with special needs , supplying buses to transport them out of town .

Voluntary evacuations were issued in San Patricio and Victoria counties and parts of Jackson County , according to the governor 's office .

More than 1,300 inmates from the Texas Correctional Institutions Division 's Stevenson Unit in Cuero were being evacuated to facilities in Beeville and Kenedy , Perry 's office said , and 597 were transferred from the substance abuse Glossbrenner Unit in San Diego , in south Texas , to Dilley .

Naval air stations in Texas also began to prepare for Hurricane Ike 's expected arrival . Naval Air Station Kingsville was to begin moving about 50 aircraft to El Paso , San Antonio and Fort Worth on Wednesday afternoon , the public affairs office there said . Naval Air Station Corpus Christi will also move about 75 aircraft to other Texas locations , its public affairs office said .

Evacuations appeared to have saved lives in Cuba when Ike slammed into the island . Four deaths were reported from the storm , according to the Cuban government . The Cuban Civil Defense brought buses or trucks to take people to shelters . See the damage from the storm ''

Cuban state television reported that two people were killed when they tried to remove an antenna , The Associated Press said . One man died when a tree crashed into his home , and a woman died when her home 's roof collapsed , according to the AP .

The storm shredded hundreds of homes and caused some dilapidated buildings in Havana 's older areas to collapse , the AP reported . Watch as winds and waves pound Cuba ''

The United States , which provided $ 100,000 in emergency aid to communist-run Cuba through private aid agencies after Hurricane Gustav hit the island August 30 , said Tuesday that it was considering additional emergency aid for Cuba because of Ike .

Also , the United States said it will lift restrictions on cash and humanitarian assistance sent to Cuba for the next 90 days . The move will allow nongovernmental organizations to provide assistance and cash donations .

The storm pounded Grand Turk Island in the Turks and Caicos chain , putting a strain on the British territory 's tourism industry . Watch houses lie in heaps on Grand Turk ''

Flooding and rains from Ike 's outer bands have been blamed for 70 deaths in Haiti . Watch the devastating aftermath ''

CNN 's Mike Mount contributed to this report .

Copyright 2008 CNN . All rights reserved.This material may not be published , broadcast , rewritten , or redistributed . Associated Press contributed to this report .

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Texans in low-lying areas and mobiles homes urged to get out